1. Field of the Invention
This invention relates to a plug valve, more particularly, to a rising stem single or dual (i.e., stacked) plug valve of the type typically used in dual canister strainer assemblies and as diverter valves.
2. Description of the Prior Art
Plug valves are quite well-known in the art. U.S. Pat. Nos. 2,215,853 and 2,893,681 both to McNeal teach stacked tapered plug valves for two-canister strainers. Stacked, simultaneously operated tapered valves wherein each valve member has an individual taper are disclosed in U.S. Pat. Nos. 3,595,270 to McNeal, Jr. and 3,679,060 to Smith.
U.S. Pat. Nos. 3,499,467 to McCord et al.; 3,768,654 to Pearce; 4,355,659 to Kelchner; and 5,102,543 to Burroughs teach a variety of stacked valves having O-rings or other sealing members positioned between the two valves to maintain a sealing separation between these elements.
The General Twin Seal(trademark) valve by General Valve Company is a rising stem stacked plug valve having seating slips mounted independently on the tapered plug. The seating slips have O-rings located on the outer surface which interact with the valve body to create a seal. The slips have openings that correspond to the plug valve openings. The O-rings are forced into contact with the valve body during seating of the plug. The slips create a double seal around the openings through O-ring contact and metal to metal contact.
The prior art teaches rising stem plug valves wherein each valve is tapered. However, in a rising stem dual plug valve it is undesirable to locate an O-ring for sealing separation between the plug valves and tapered portion of the plug body between the individual valves.
Most of the prior art relies on surface to surface contact of the plug and the valve body to create a seal around the plug openings. For example, consider U.S. Pat. No. 2,001,035 to Noll illustrating a conventional metal to metal seal for a plug valve. When both bodies are metal, this seal is not always adequate. The General Twin Seal(trademark) valve relies not only on surface to surface contact, but also on O-rings. However, the O-rings are located on an independent slip that communicates with the plug and valve body. U.S. Pat. No. 4,726,391 to Barra discloses a complex valve in which each part is surrounded by grooves which receive U-shaped sealing members. The U-shaped sealing members include a passage to transmit leakage. The passage minimizes the total sealing area of the sealing member. The U-shaped sealing member also includes open areas adjacent the valve body to allow for deformation of the sealing portions. These open spaces minimize the support or backing for the sealing portions.
Conventional rising stem plug valves utilize a handle or wheel to raise and lower a stem coupled to the plug in order to unseat and seat the plug within the valve body. While this is practical in some applications, the degree of freedom is somewhat limiting.
It is an object of this invention to provide a rising stem plug valve assembly comprising an improved seal around each opening in the plug.
It is a further object of the present invention to provide a rising stem dual plug valve wherein the plug comprises an untapered portion between the upper and lower portions of the plug.
It is yet another object of the present invention to provide a greater degree of freedom for raising and lowering the plug during unseating and seating of the plug(s) into a valve housing.
The valve assembly of the present invention is a rising stem plug valve including a valve housing, a plug(s), a handle for rotating the plug between operative positions in a conventional fashion, a stem, and an assembly for unseating and seating the plug within the valve housing. The valve assembly may be a rising stem single plug valve wherein the plug has plug openings to form at least one valve that may be a tapered plug valve. The valve assembly may be a rising stem dual plug valve wherein the plug has integrally formed upper and lower portions each of which have plug openings and may be tapered forming a tapered plug valve.
In the rising stem dual plug valve of the instant invention, positioned between the upper and lower portions of the plug is an O-ring on a straight, untapered portion of the plug. The O-ring maintains fluid separation between the upper and lower portions of the plug, even as the plug is raised.
A control assembly, for example a ratcheting assembly, is coupled to the stem, for example a threading screw. The stem is in turn coupled to the plug. This construction allows for the unseating and seating of the plug within the valve body.
Sealing ring cords, preferably rectangular in cross-section, substantially surround each plug opening thereby creating an improved seal around each opening.
The plug interior pattern between the plug openings of the present invention may be one of many cross-sectional configurations to allow for different flow patterns depending on the application of the valve assembly. In the rising stem dual plug valve of this invention, the upper and lower portions of the plug may have different interior configurations.